Nature Notes
Watch Out For Mackinac Chipmunks When Bicycling
By Patricia Martin

One of the things I like about living on Mackinac is that one is never far away from the natural world. Whether it be the power of a thunderstorm and the winds on the water, Great Blue Herons flying by the bluff while you walk to the barn, Cardinals, crows, and gulls calling, young coyotes trotting down the road, those darn Eastern Cottontails chewing on your garden, slugs, butterflies, earwigs, squirrels, and spiders, nature is all around us, whether we like it or not. You just have to keep your eyes and ears open and be aware of the world around you.

There are times, however, when you just literally run into nature. Such an incident happened to a colleague at this paper several weeks ago. As she was biking down the road, a chipmunk ran out onto the street and she hit it, or it hit her bike, so she asked me to write about these cute little rodents in its honor.

The Eastern Chipmunk (Tamias stratus) is probably the Chipmunk she encountered. The Least Chipmunk (Tamias minimus) is also found in our area but it's not nearly as common as the Eastern. Most people around here have seen Eastern Chipmunks numerous times, as they seem to deal well with people.

The Eastern Chipmunk is about nine to 10 inches in length with the tail making up 2.5 to 4.5 inches of its length. They don't weigh very much, only two to four ounces. The back of this chipmunk is grayish to reddish brown with a definite red patch on the rump. The under parts are white and along the back are five dark stripes, the longest of which runs along the midline. Between the paired lateral dark stripes are narrow bands of white. These stripes help to distinguish this rodent from others in the region, except for the smaller Least Chipmunk, but their stripes extend to the tail, while the stripes on the Eastern Chipmunks don't cross the rump.

The Eastern Chipmunks are the most common chipmunk in North America and they're often called ground squirrels as they build burrows underground. They usually like to inhabit open deciduous forests where stumps, downed logs, and rocks provide them cover. Their most favored habitat is a beech-maple forest, but they will also live in brushy areas and coniferous forests, They usually avoid swampy places.

Around here, I see them commonly around my barn, which is in a cedar woods, but also around my house. They seem to like my wood pile and all the cover that the shrubs in my garden provide. They've even been known to burrow under buildings or abandoned stone foundations. In addition, they've been known to enter houses.

When I was young, one got into our cottage at Silver Birches. We were trying to catch it and my brother, in his pajamas, tried to block the hallway. That little fellow ran up my brother's leg inside the pajama pants and exited out on his shoulder. Boy, did my brother scream, which I think scared the chipmunk and it ran into a small room, where we cornered it, collected it in a waste basket, and let it go outside.

As far as the burrows of the Eastern Chipmunk go, the chipmunk digs a tunnel less than a yard below the surface that can be up to 33 feet long and consists of interconnecting galleries. One room is set aside as a nesting site in which crushed or chewed leaves are used to make a footwide bed. Other chambers in the burrow are used to store food and debris. The opening to the burrow is sometimes hard to find, as it's only a couple of inches in diameter and there is no dirt piled up around it. Instead, the dirt from digging the burrow is distributed evenly around the hole or used to close up old entrances.

Chipmunks are most active in the middle of the day, mid-morning to mid-afternoon, and they're quite solitary. They're also territorial and will defend their burrow. If an invading chipmunk comes into an Eastern Chipmunk's territory, it will usually threaten the intruder visually and vocally before giving chase. They often become so involved in getting the invader that they ignore other things around them, be they human or canine.

These rodents usually forage for food along the ground, but they will also climb trees, shrubs, and fences to get breakfast. Like many rodents, they eat a variety of dietary staples, including fruits, seeds, and nuts, along with mushrooms, insects, earthworms, slugs, and bird eggs. The chipmunk will transport dry food items back to its burrow in its cheek pouches, which can hold hundreds of seeds when filled. These rodents store food all year, but like many Mackinac Islanders, they're particularly active in storing their larder in the fall for the upcoming winter. Though these animals are less active in winter and do go into torpor, they really don't have the fat storage that would allow them to be true hibernators. Instead, they have to rouse periodically to snack on their hoarded food, and perhaps even forage outside during a mild winter.

Like all rodents, chipmunks have a single pair of curving incisors on the upper and lower jaws with a large gap separating the incisors and the cheek teeth. The incisors grow throughout the life of the rodent and are continually worn down by use. The front surface of the teeth are usually a yellow to orange enamel, which is much harder than the dentine on the back surface of the incisors, which allows the teeth to continually be sharpened. This allows the animal to chew or even chisel through tough materials such as feed bags, in order to get food.

Eastern Chipmunks usually reproduce twice a year, once in the spring and again in mid-summer. Each time they produce two to five blind, hairless young, which only weigh in at a tenth of an ounce and are weaned about a month and a half later.

These rodents are dinner for a whole variety of predators. Most diurnal hunting mammals enjoy them, including many of the weasels, lynx, bobcat, red fox, and coyotes. Many of the large raptors, such as the red-tailed hawk and goshawk, feed on this rodent. Some of the domesticated animals, such as cats and dogs, enjoy a good Eastern Chipmunk dinner.

Once, I was looking out my window and saw my dog laying down in the yard with something between his front feet. When I got close enough, I could see it was a chipmunk that wasn't moving. I put my dog inside and got a shovel so I could pick it up and bury the poor thing. The chipmunk then looked up, saw the shovel, and took off. Those little guys are trickier than you'd think.

Although chipmunks can live up to eight years in the wild, they usually only live a couple.

Keep an eye out for these little furry fellows. They're rather cute. Oh, and by the way, try not to hit them with your bike. They have enough animals trying to get them.

Trish Martin is a year-around resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.